1. Field of the Invention
This invention relates to an engine control apparatus wherein a cylinder discrimination control is performed on the basis of, for example, the crankangle signals of the crankshaft and the cam signals of the camshaft of an engine. More particularly, it relates to an engine control apparatus which prevents the stop of cranking at the time of start and any erroneous cylinder discrimination at restart, thereby to reliably restart an engine, and which protects a starter starting motor (starter).
2. Description of the Related Art
In general, in a vehicular engine, there has been known an engine control apparatus wherein, in order to optimally control fuel injections and ignition timings for a plurality of cylinders in correspondence with running conditions, individual sensors for generating the crankangle signals and cam signals of the engine are disposed, and the cylinders are discriminated, and a fuel injection control and an ignition timing control are performed, on the basis of the outputs of the sensors. Besides, in recent years, the engine control apparatus has come to adopt the larger number of teeth of a crankangle signal plate for the calculation of the crankangle of the engine in order to perform a faster and more delicate fuel control as well as ignition control. A cylinder discrimination control has become a higher degree and more complicated, and a very large number of control development man-hour has been expended on a control development concerning the cylinder discrimination.
In starting the engine, a starting motor (hereinbelow, also termed “starter”) for driving the engine as uses a battery as a power source is employed in order to bring the engine into a complete explosion.
The starter consists of a pinion which meshes with a ring gear fixed to a crankshaft, and a motor portion which feeds a rotating force to the pinion. Incidentally, a starting motor relay for ON/OFF-controlling power feed to the motor is disposed.
During cranking at the engine start, the starter is driven, whereby the engine starts rotating, and an engine control unit (hereinbelow, also termed “ECU”) performs the cylinder discrimination. In this regard, the driver of a vehicle erroneously turns OFF a starter switch rarely. Further, at low temperatures, it is sometimes the case that a reliable combustion is not attained, and that the so-called “complete explosion” is not reached even when the starter is driven for a while, so the engine stops due to starter-OFF.
More specifically, when a piston fails to ascend to a compression top dead center due to the starter-OFF during a compression stroke, it descends immediately before the top dead center, and the engine causes a reverse rotation and then stops.
Further, on this occasion, in a case where the driver has tried restart during the engine reverse rotation or immediately before the engine stop, the cycles of the crankangle sensor signals become unequal intervals at the start of the engine rotation based on the starter drive at the time of the restart. In some cases, accordingly, the engine control unit cannot properly discriminate the cylinders, and the ignition control and the fuel injection control cannot be performed for the appropriate cylinders, so that a restartability worsens.
Moreover, the inferior meshing of the pinion sometimes occurs on account of an engine forward rotation and the engine reverse rotation based on the starter drive or the jump of the pinion into the ring gear being rotating.
In view of such drawbacks, JP-UM-A-53-37838 (hereinbelow, termed “Patent Document 1”) has proposed in a circuit wherein a starter is operated by a starter switch, a starter protection apparatus in which once the starter switch has been opened, the starter is prevented from operating for a certain fixed time period.
Besides, JP-A-10-318106 (hereinbelow, termed “Patent Document 2”) has proposed a starter protection apparatus in which the operation of a starting motor is continued during the actuation of a starter switch, whereby an engine is reliably started, and in which the operation of the starting motor is suppressed even when the starter switch is actuated during the rotation of the engine or immediately after the stop of the engine, whereby a starter pinion is prevented from jumping into a ring gear being rotating.
As described above, in the prior-art apparatus, in the case where the “ON” and “OFF” of the starter attributed to any of various engine starting environments or the actuation of the starter switch have been repeated during the cranking at the start of the engine, the cycles of the crankangle sensor signals become the unequal intervals, and hence, the cylinders are not discriminated properly. As a result, the fuel injection control and the ignition timing control become different from desired ones, and the restartability worsens. In the worst case, a backfire and a starter lock might be incurred.
Besides, when the starter is driven again, the starter pinion jumps into the ring gear being rotating due to the engine forward rotation or the engine reverse rotation, whereby the starter pinion undergoes a large load in meshing with the ring gear, and the damage of the gear or the starter lock occurs. In the worst case, a situation where the restart is impossible can occur.
Further, in the starter protection apparatus stated in each of Patent Documents 1 and 2, once the starter switch has been opened, the starter cannot be driven for the certain fixed time period. Therefore, in a case where the engine could not be started by the preceding actuation of the starter switch, it cannot be restarted till the lapse of the fixed time period, even if it is in a completely stopped state. That is, however high an engine revolution speed at the time of the failure of the first start may be, the fixed time period needs to be waited. This leads to the problem that, since the starter does not rotate at the restart, an uneasy feeling is inflicted on the driver.